The alkylation of paraffins with olefins for the production of alkylate for gasolines can use a variety of catalysts. The choice of catalyst depends on the end product a producer desires. Ionic liquids are catalysts that can be used in a variety of catalytic reactions, including the alkylation of paraffins with olefins. Ionic liquids are primarily mixtures of salts which melt below room temperature, and will form liquid compositions at temperature below the individual melting points of the constituents.
Ionic liquids are essentially salts in a liquid state, and are described in U.S. Pat. No. 4,764,440, U.S. Pat. No. 5,104,840 and U.S. Pat. No. 5,824,832. The properties vary extensively for different ionic liquids, and the use of ionic liquids depends on the properties of a given ionic liquid. Depending on the organic cation of the ionic liquid and the anion, the ionic liquid can have very different properties. The behavior varies considerably for different temperature ranges, and it is preferred to find ionic liquids that do not require operation under more extreme conditions such as refrigeration.